Insulating a roof from inside is technically feasible; it’s what’s called the “cold roof” principle. This system was often used in the past, but is not recommended nowadays. In fact, it may cause damage in the long term.
What’s the solution? Go for a “hot roof” or external insulation.
To produce a cold roof, the insulation has to be fitted inside below the weatherproofing support (beams, brickwork, etc) with a ventilated air gap.
Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation.
To produce a hot roof, rigid insulation is fitted outside, above the weatherproofing. This is then covered with a further weatherproofing layer.
Although cold roof systems were used extensively in the past, they are now considered out of date and are highly inadvisable. In fact, insulation from the inside will inevitably lead to the formation of condensation caused by the humidity present inside the building.
As a consequence:
Is there an efficient method to prevent the accumulation of humidity? Installing a vapour barrier membrane over the insulation is not enough to stop the migration of vapour. The air gap intended to ventilate the insulation isn’t efficient either. In fact, it can actually aggravate the problem; as the weatherproofing supports are often colder than the outside air, condensation forms there as well, and adds still more to the humidity.
So you see, insulating from outside, using a hot roof system, is the best option. Call in a specialist contractor to do the work!
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